Hitherto, there have been proposed various kinds of conveyor line systems configured to convey conveying containers, to which thermoreversible recording media are attached as recording parts, in a predetermined conveying direction and configured to irradiate the thermoreversible recording media with laser light to rewrite images (see, for example, Patent documents 1, 2, and 3).
The conveyor line systems include image erasing devices configured to irradiate thermoreversible recording media, in which images have been recorded, with laser light to erase the images; and image recording devices configured to irradiate the thermoreversible recording media, from which the images have been erased by the image erasing devices, with laser light to record new images. Note that, the image erasing device and the image recording device may be collectively referred to as an image processing device.
It is desirable to accurately irradiate only the thermoreversible recording media with the laser light when the images are recorded in the thermoreversible recording media or the formed images are erased by irradiating the thermoreversible recording media with the laser light. Displayed images such as company logos, alarm displays, instructions, and barcode images are drawn on the conveying containers to which the thermoreversible recording media are attached. The displayed images formed on the conveying containers can improve handling property, safety, etc. of the conveying containers.
In the conveyor line systems, however, not only the thermoreversible recording media but also the conveying containers surrounding the thermoreversible recording media or the displayed images drawn on the conveying container may be irradiated with the laser light.
When the displayed images are irradiated with the laser light, the displayed images may be scraped depending on materials of the displayed images because the materials of the displayed images absorb the laser light. As the materials of the displayed images melt or sublimate by repetitive irradiation of the displayed images in the conveying containers with the laser light, the surfaces of the displayed images are gradually scraped. This raises a problem with deterioration in visibility or machine readability of the displayed images.
Even in the case of using thermosensitive recording media for single use, the above problem would arise when the conveying containers are repeatedly used. Also, depending on the relationship between absorbance of the recording part and absorbance of the image part, in which the displayed image is drawn, at a wavelength of the laser light emitted by the image processing device during image recording, even when the image part is irradiated with the laser light only once, for example, confidential information is unintentionally recorded on the image part in which the displayed image is drawn. This may raise a problem with leakage of confidential information.
Two cases are considered as reasons why the displayed image is unintentionally irradiated with laser light.
The first case is that a thermoreversible recording medium has not been attached to a position to be irradiated with laser light for the following reason, for example: the thermoreversible recording medium attached to the conveying container has been peeled; a conveying container with no thermoreversible recording medium attached has been included by accident; or a worker for putting the conveying container has mistaken a direction of the conveying container.
The second case is that a position of the thermoreversible recording medium and a position to be irradiated with laser light have been mismatched for the following reason, for example: there has been an error in positioning information for changing the laser light irradiation position per conveying container in the case where conveying containers included are different in at least one of a size and a shape and as a result the relative positions of the thermoreversible recording media attached to such conveying containers with respect to the image processing device are also different during at least one of image recording and image erasing; a position of the conveying container placed on the conveyor line has been misregistered; the thermoreversible recording medium attached to the conveying container has been shifted from an appropriate position; the conveying container conveyed at high speed has exceeded a stopper with excessive momentum; or the conveying container has been moved back in the opposite direction to the conveying direction as a result of being bumped into a stopper with excessive momentum to cause reaction against the stopper.
A rate of the misregistration caused in the aforementioned cases changes depending on performances of the conveyor line for use or the conveying container for use, but this rate is about 10 or less relative to 100 conveying containers. In view of the above, it can be considered that when the thermoreversible recording medium attached to one conveying container is irradiated with laser light emitted to rewrite an image in the thermoreversible recording medium, the laser light is emitted to the conveying container or the displayed image at most 1/10 times relative to the number of times of repetitive rewritings.
Meanwhile, in order to record as much information as possible on the thermoreversible recording medium, the information is recorded on the entire surface of the thermoreversible recording medium. Therefore, when the misregistration occurs, the laser light emitted to record information on the edges of the thermoreversible recording medium is also emitted to the conveying container. Also, in the case where the image on the thermoreversible recording medium is erased, the entire surface of the thermoreversible recording medium is irradiated with laser light in order to erase the information recorded on the entire surface of the thermoreversible recording medium. If the misregistration occurs, therefore, laser light emitted to erase the information of the edges of the thermoreversible recording medium is also emitted to the conveying container or the displayed image.
A high throughput has been desired for the conveyor line system. To this end, a conveying speed of a conveying container needs to be set as high as possible. Therefore, a conveying container is bumped into a stopper with momentum, a misregistration becomes significant. In this case, a problem that the conveying container or the displayed image is irradiated with laser light particularly easily arises.
As for one exemplary method for solving the aforementioned problem, there has been proposed a method in which a sensor configured to detect a thermoreversible recording medium is disposed on a conveyor line and, when the thermoreversible recording medium is not detected, laser light is not emitted at equal to or above a predetermined power (see Patent document 4). This method can suppress a conveying container or a displayed image from being irradiated with laser light when a thermoreversible recording medium is not attached to a position to be irradiated with laser light.
In some cases, however, the position of the thermoreversible recording medium and the position to be irradiated with laser light are misregistered. Therefore, the problem that the displayed image in the conveying container is deteriorated in visibility and machine readability by irradiating the displayed image drawn on the conveying container with laser light has not yet been solved.
Therefore, there is a need for provision of a conveyor line system capable of preventing deterioration in visibility and machine readability of an image part of a conveying container, in which a displayed image is drawn, the deterioration arising as a result of irradiation of the image part of the conveying container with laser light.